[February 14th]
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Question:
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3,9,13,15,18,7,20,1,4,14,5,21,6,2,17,10,8,16,12,11,19
Please input the flag with no spaces! :)

Answer
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1. This seems to be a normal nr 3 is 1 letter = W
2. I was right, posting picture for easily understanding the task:


Flag:
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WELLIAMGLADTHATISOVER

Original writeup (https://github.com/str0nkus/NeverlanCTF-2019-Writeups/tree/master/Crypto/February%2014th).